I'm being told to navigate through certain folders, such as UnrealEngine3 or TryGame folders via the steam directory or My Games, in order to find config files that would let me change my windowed/fullscreen and resolution data. I don't know which path to take now, since there are so many different guides sending me to so many different places that don't work.

The config files are in My Documents\My Games\AbyssOdyssey\AOGame\Config I believe.Maybe try re-running the installers in Steam\steamapps\common\abyss_odyssey\_CommonRedist too - I think some may have been added/updated when Windows 10 was released.